1. Technical Field
The present invention relates to a converter and a measurement apparatus.
2. Related Art
Conventional ultrasonic detection is known for generating an image showing the internal structure of a measurement target, such as a living organism, by irradiating the measurement target with ultrasonic waves and detecting the ultrasonic waves reflected from the measurement target. This type of ultrasonic detection uses a converter that converts the detected ultrasonic waves into electrical signals using a plurality of piezoelectric elements, as shown in Patent Documents 1 to 3, for example.    Patent Document 1: Japanese Patent Application Publication No. 2002-101496    Patent Document 2: Japanese Patent Application Publication No. 2004-112326    Patent Document 3: Japanese Patent Application Publication No. 2002-142294
A photoacoustic technique of irradiating a measurement target with light of a prescribed frequency is known as a method for measuring a measurement target with ultrasonic waves from the measurement target. With the photoacoustic technique, a periodic temperature change in the measurement target is created by the radiated light, and detecting the ultrasonic waves caused by fluctuation of the measurement target. With the photoacoustic technique, a converter is used to convert the detected ultrasonic waves into electrical signals.
However, with the photoacoustic technique, the intensity of the ultrasonic waves output from the measurement target is significantly lower than the intensity of the ultrasonic waves reflected by the measurement target during the ultrasonic wave detection. For example, the intensity of the ultrasonic waves detected using the photoacoustic technique are approximately 1% of the intensity of the ultrasonic waves detected using the ultrasonic wave detection. Therefore, the converter used for the photoacoustic technique must reduce external noise, electrical signal loss, and crosstalk between electrical signals, for example.
A conventional converter is known that transmits electrical signals from piezoelectric elements to cables through film wires. Furthermore, a conventional converter is known that transmits electrical signals from piezoelectric elements through via wires provided in a backing member of the piezoelectric elements. However, with film wires and via wires in the backing member, it is difficult to control the impedance and shield the transmission path, and therefore signal crosstalk and the like occurs in the film wire portion.